Hagedorn temperature and physics of black holes

TL;DR

This paper reviews the role of the Hagedorn temperature in string theory and its implications for black hole physics, including entropy calculations and holographic models, highlighting the necessity of fundamental strings for consistent black hole theories.

Contribution

It presents a recent approach to calculating black hole entropy using fundamental strings and explores the implications for holographic large-N gauge theories.

Findings

Entropy of large black holes estimated via fundamental strings

Hagedorn temperature as a limiting temperature in string models

Implications for black hole thermodynamics and holography

Abstract

A mini-review devoted to some implications of the Hagedorn temperature for black hole physics. The existence of a limiting temperature is a generic feature of string models. The Hagedorn temperature was introduced first in the context of hadronic physics. Nowadays, the emphasis is shifted to fundamental strings which might be a necessary ingredient to obtain a consistent theory of black holes. The point is that, in field theory, the local temperature close to the horizon could be arbitrarily high, and this observation is difficult to reconcile with the finiteness of the entropy of black holes. After preliminary remarks, we review our recent attempt to evaluate the entropy of large black holes in terms of fundamental strings. We also speculate on implications for dynamics of large-N gauge theories arising within holographic models.